Recently, the effect of ultraviolet on the skin has become widely known recently, and users have become increasingly conscious of skin whitening. Thus, there is demand for a cosmetic which provides a higher UV protection ability and even a good feeling in use.
Due to the fact that an O/W emulsified composition can provide refreshing and light fresh feeling in use while it contains oils, such emulsified composition is widely used not only in cosmetics for basic skin care such as milky lotions and creams, but also in products such as foundations and sunscreen cosmetics.
In cosmetics, UV protection ability has been often provided by incorporating organic UV absorbers or inorganic UV scatterers such as fine particle titanium oxide and fine particle zinc oxide. However, when a high UV protection ability is tried to be provided over a wide range of UVB to UV-A by incorporating a large amount of inorganic UV shielding powder such as fine particle titanium oxide and fine particle zinc oxide, the finish may become whitish, or frictional or powdery feeling may be caused.
In contrast, many organic UV absorbers are generally highly polar oils and do not cause the problems such as the whitish finish and frictional powdery feeling mentioned above. However, they provide stickiness so much to deteriorate the refreshing feeling of O/W emulsified composition when the emulsified composition is applied to skin. In addition, the emulsion stability tends to decrease. For example, though octocrylene and ethylhexyl methoxycinnamate achieve an excellent UV absorption, it has been difficult to obtain an O/W emulsified composition containing them with a high emulsion stability and a good feeling in use.
It is a common technique to incorporate a silicone oil in a cosmetic to decrease the stickiness. However, there has been a problem that the emulsion stability became significantly deteriorated when an O/W emulsified composition was prepared by mixing a highly polar oil such as an organic UV absorber with a silicone oil.
Also, when an oil-soluble solid component was used by being dissolved in an oil phase, there has been a problem that the polarity change of oil phase due to incorporation of a silicone oil causes precipitation of the solid component.
For example, bis-ethylhexyloxyphenol methoxyphenyl triazine is a highly excellent organic UV absorber because of its UV absorbing ability in a wide range of UV-A to UV-B. It is a crystalline solid at ordinary temperature and is generally used by being dissolved in a highly polar oil. However, bis-ethylhexyloxyphenol methoxyphenyl triazine sometimes precipitates owing to the incorporation of a silicone oil. Thus, it has been difficult to incorporate stably bis-ethylhexyloxyphenol methoxyphenyl triazine in an O/W emulsified composition containing a silicone oil.
Patent Literature 1 describes an O/W hair cosmetic containing two oil phases as follows:
(1) an oil phase (hard oil phase) having the average particle size of 0.5 μm or less formed with a nonionic surfactant which is solid at ordinary temperature and has the Krafft point of 40° C. or more; and
(2) an oil phase (soft oil phase) having the average particle size of 0.5 to 100 μm formed with a surfactant and/or an alkyl-modified carboxyvinyl polymer.
However, even in such an O/W emulsified composition, it has been difficult to incorporate stably the organic UV absorber as mentioned above and a silicone oil.